In an animal model of endotoxin induced diffuse lung injury, we propose to investigate the hypotheses that the pathogenesis of the injury involves oxidant injury to the lungs, an endotoxin induced proteinase/antiproteinase imbalance and alterations in cyclic nucleotide metabolism. Further, we propose that eicosanoids and platelet activating factor (PAF) released as part of the inflammatory response to endotoxemia mediate alterations in lung function and interactions of inflammatory cells with the lungs. To test these hypotheses, we propose studies which will measure lipid peroxidation products in blood and lung lymph and antioxidant enzymes in lung tissue after endotoxin and determine effects of exogenous antioxidants and induction of endogenous antioxidants on the endotoxin response. We will measure a panel of proteinases and antiproteinases in bronchoalveolar lavage (BAL) fluid, blood and lung lymph and determine effects of depletion (chloramine-T) or enhancement (alpha-1-antitrypsin) of antiproteinase activity on the responses of the lungs to endotoxemia. We will measure effects of endotoxin on release of eicosanoids and platelet activating factor in the lungs and determine effects of drugs which inhibit such release on the endotoxin reaction. We will collect lymphocytes and alveolar macrophages from sheep given endotoxin for in vitro measurements of chemotaxin, eicosanoid and PAF production. We will define the trafficking of neutrophils, lymphocytes (including subsets) and macrophages in blood, lung lymph, BAL fluid and lung tissue during the response to endotoxin and determine effects of interventions which alter the pathophysiology of the response on inflammatory cell traffic. We will determine the mechanism of suppression of the lungs' response to endotoxemia by prostaglandin E2. Finally, we will determine whether pharmacologic manipulation of cyclic nucleotide metabolism will prevent or reverse the increase in lung vascular permeability caused by endotoxemia. These studies, combined with others in this proposal, will permit a definition of the pathogenesis of endotoxin induced lung injury and demonstrate rational approaches for therapy and prevention which may be useful in humans.